Fluid pressure braking system



- motors-24 for actuating biwak'es 26. Th

Patented" S ept. 8,1 1942 umrso STATES PATENT OFFICE FLUID raasscn'n BRAKING SYSTEM Erwin F. Lowelre, Detroit, Mich, assignor to Bydraulic Brake Company, Detroit, Mich.,'a corporation of California Application August 16, 1940, Serial No. 352,915

- In Canada October 10. 1939 This invention relates to fluid pressure systems, and more particularly to. fluid pressure braking systems for-motor vehicles.

An object of the invention is to provide a fluid pressure braking system including a fluid pres- 5 .sure producing deviceot the two-phase type operative to compound pressure on the fluid in thesystem without proportionately increasing the applied activating force.

- Another object of. the'invention is to provide =l a fluid" pressure producing. device of the twophase type operative to eiiectatransition from low to" high pressure upon a predetermined movement. 1 Anotherobject of the invention is to provide -1' f a low pressure producing means and a high pressure producing means, and associated means.

for locking the low and high pressure means together during the initial movement thereof and thereafter to gradually disconnect the low'20 and high pressure means and to lock the lowpressure means against movement. d

Other objects and advantages of the inven tion will appear from the following description taken in connection with the accompanying drawing forming a partnf this specification, and in which: n v r Fig. 1 is 'a schematic'viewof a fluid pressure braking system embodying the invention;

Fig. 2 isa vertical sectional view'of the fluid pressure producing vdevice "embodied in the system; o v

Fig. 3 is a sectional view substantially on line 3 -8, Fig. 2; and

Fig. 4 is a sectional view'oi' a two-way valve. Referring to the drawingior more sp'eciflc d-'" tails of the inventioma fluid pressure braking system-illustratedin Fig.1 includes a'fluid pres! sure producing device indicated generally at [9.

-This-device is of the two-phasettype; operative to compound pressure on the fluid in the: system,

without proportionately increasing the applied activating force. j 4

This fluid pressure producing device may be rockable on a stub shaft 14. A roller 16 on the I lever serves to transmit force to. the. compression- .element of the device, and a spring 18 'connecting the lever to a fixed support20 serves to return the lever to its retracted position. v

A jfluid'pressure delivery pipe or conduit, 22 suitably connected to the discharge-port of the fiuidn ressure producing device has branches connected respectively to fluid pressure actuated activated by a conventionai foot vpedal'lever' i2 are preferably arranged in one pair for actuating the brakes associated with the iront wheels 0! the vehicle, and another pair for actuating the brakes associated with the rear wheels of the vehicle.-' The brakes may be 0! any preferred structure.

The fluid pressure producing device ll includes a reservoir 28 having a fllling opening 3. normally closed by a plug 32 having bpenings 2| therethrough for venting the reservoir to the atmosphere. A cylinder 26 in one'end of the reservoir has one of its ends opening through the top of the reservoir and its other end opening into the reservoir adjacent the bottom thereof, and a cylinder 38 depending from the bottom o! the reservoir in axial alignment with the cylinder 36 has one of its ends opening into the reservoir as at 0 and its other end closed ,as by a head 42 provided with a discharge port ll controlled as by ,a two-way valve 6 seated on the. head 42. The diameter of the cylinder 28 is-larger than that of the cylinder 36, and at the adjacent ends of the cylinders is a shoulder 48. Thecylinder 38 has an internal circumi'erential groove 50, and a portion oi! its wall defining this groove tapersjrom the bore oi! the.

cylinder downwardly and outwardly as indicated at 52 to approximately the bottom of the groove.

" A compound piston 54 reciprqcable in the cylinder 88 includes a low pressure piston it and a high pressure piston 58. The low pressure piston comprises a hollow cylinder shell having substantially medially of. its length a plurality of spa ed openings Bl for the receptionoi balls 82. s lowpressure piston seats, when in its retracted position, on the shoulder 48, and seated on its head is'an annular sealing cup. held against displacement by a spring 66 interposed between the cup and the head 42 of the cylinder 38. The spring 66 serves also to return the piston 58 to its retracted position. The high presi sure piston 58 'reciprocable in the .low pressure piston 56 has substantially medially of its length ascircumferential groove -68 for'the reception of the balls 62, and'a portion of the wall defining this groove tapers from the perimeter; of the "piston inwardly and downwardly as indicated at 70- to substantially the bottom of the groove. The high pressure piston .68 has on its'ghead-a concentrically disposed spring seat 12, and an axial passage .N providing communicationibe-;

tween the reservoii'. and that portion of the cylinder 38 forward oivthe piston. A spring II M h interposed between the spring 12.01am e motors 5v head of the piston 50 andthe two-way'valve-li controlling the discharge port. serves to normally retain the valve on its seat and also to i 88 terminating in a conical head 88 adapted to enter and close the passage 18 through the'high pressure piston 88.

In a normal operation, the applied activating force on the plunger 18 results in advancing the ,plunger against the resistance of the retractile and the consequent actuation of the brakes with increased force and without perceptible increase in the applied activating force.

Upon conclusion of a braking operation and release of the applied activating force, the plunger 18 returns to its retracted position under the influence of the retractile spring 82. This results in release of the piston and establishing communication between: the reservoir 28 and that portion of the cylinder 88 forward of the piston by way of opening the. passage 18,

, through the high pressure piston and also respring 82. During the initial movement of the plunger 18, the conical head 88 on the extension 88 of the plunger enters and closes the passage ,18 through the high pressure piston 58, so as' to close communication between the reservoir and that portion of the cylinder 38 forward'of the pistons.

Thereafter, as the plunger 18 advances, the low-and high pressure pistons 56 and 88 move in unison for a predetermined stroke depending upon the location of the detent or circumferential groove 58 in the wall of the cylinder 38. Because of a differential in the areas of the low and high pressure pistons, there is a tendency toward relative movement between these pistons 58 and 58. This tendency is resistedby the locking action of the balls 62 seated in the openings 88 in the wall of the'low pressure piston and in the groove 88 in the circumference of'the high pressure piston until the openings 88 register with the detent or groove 80 in the'wall of the cylinder 88, and, thereafter, as the pistons 88 and 88 advance on thecompression' stroke, the inclined surface partially defining the groove 88 in the circumference of the high pressure piston 88 urges the balls 82 against the inclined surface 52 partly defining the groove 58 in the wall of the cylinder as until the balls are seated in the groove 88 and effectively lock thelow pressure piston against further movement.

During this operation, fluid in the cylinder 38 forward of the pistons is displaced therefrom,

past the two-way valve 88, through the discharge port 88 and fluid pressure delivery pipe or conduit 22 into thefluid pressure actuated motors 28, resulting in energization of the motors and the consequent actuation of the friction elements of the brakes 28. v

The locking action'of the low pressure piston against advance movement is effected over a. .wide range, due to controlled movement of the balls 82-by the cooperating inclined surfaces '82 and I8, and during this controlled locking action there is a slight differential in the rate of movement of the low and high pressure pistons. Because of these factors, the transition from low to high pressure is effected in small increments tending to smooth out the operation to such an extent that the transition is not perceptible to the operator.

When the low pressure piston 88 is locked against further advance, the high pressure piston l8 proceeds independently. throughout the remainder of the compression stroke, andfluld in the cylinder 88 forward of the piston is displaced therefrom, past the valve 88, and through the discharge port 88 and fluid pressure delivery pipe 22 and its branches into the motors 28,

resulting in further energization of the motors turn of the low and high pressure pistons through the influence of the retractile springs 86 and 18.

As the pistons retum to retracted position, the

high pressure piston moves in advance of the low pressure piston until the detent or groove 88 therein registers with the .openings 80 in the wall of the low pressure piston, whereupon the balls 82 are moved to their normal seat in the groove 88 and openings 88 to lock the pistons together. Thereafter, the pistons move in unison to their retracted positions, the low pressure piston seating on the shoulder 88 and the high pressure piston seating on the balls 82.

During this operation, fluid in the fluid pressure. actuated motors 28 and the fluid pressure delivery pipe or conduit 22 and its branches connectingthe motors to the discharge port 88 is returned through the port 88, past the twoway valve 88, into the cylinder. 38, under the influence of the retractile springs connecting the friction elements ofthe brakes 26. so returned to the cylinder 88 may be in excess of the capacity of the cylinder, and this excess fore, to be limited only as indicated by the scope of the appended claims.

Having thus described the various features of the invention, what I claim as new and desire to secure by Letters Patent is:

1. A fluid pressure producing device comprising a cylinder having an inner circumferential groove, ahollow piston reciprocable therein having apertures adapted to register with the groove, a piston reciprocable in the hollow piston having a circumferential groove, and means shiftable in the grooves and apertures for locking the pistons together during a predetermined movement of. the pistons and thereafter to release the pistons from one another and to retain one of the.

pistons against movement.

2. A fluid pressure producing device comprising a cylinder having an inner circumferential groove with a portion of its wall defining the groove tapered from the bore of the cylinder to the bottom of the groove, a hollow piston reciprocable in the cylinder having in its wall a plurality of spaced apertures, a piston reciprocable in the hollow piston having a circumferene tial groove with a portionof its wall defining the groove tapered from the circumference of the piston to the bottom of the groove in oppositely disposed relation to the tapered portion of the cylinder .wall, and a plurality of ball in the grooves and apertures.

3. A fluid pressure producing device comprising a reservoir, a cylinder depending therefrom having an inner circumferential groov with a portion of its wall defining the groove tapered 'shiftable upwardly and inwardly, a hollow piston reciprocable in the cylinder having a plurality of spaced openings through its well, a piston reciprocable in the hollow piston having a passage therethrough and a circumferential groove -with a portion of its perimeter tapered upwardly'and grooves and openings, and a plunger for actuating the pistons having a part adapted to enter fining the groove inclined \ipwa'rdly and inwardly 1 outwardly, a plurality of balls shift-able in the from the bottom of the groove, a hollow piston having a plurality of spaced openings through its wall adapted tocommunic'ate with the groove, a piston reciprocable in the hollow-piston having an axial passage'therethrough and a'ci'rc'umferential groove adapted to communicat with the openings with a part oi'its perimeter defining-the groove inclined upwardly and outwardly from the bottom of the groove, a plurality of balls shiitabie in the grooves and openings, and a plunger for actuating the pistons having a part adapted to enter and close the axial passage upon advance or the pistons.

5. A fluid pressure producing device comprising a cylinder, telescopic pistons reciprocabletherein, means acting upon one of the pistons to actuate it, and means coupling the second piston with the first piston for ,joint initial advance of the two pistons on the compression stroke, said means being automatically releasable upon a predetermined advance of the two pistons to permit further advance of the first piston independently of the second piston, and operable to positively lock the second piston to the cylinder to prevent the movement thereof in either direction during the independent advance of the first piston.

62A fluid pressure producing device comprismg a cylinder, telescopic pistons reciprocable therein, means acting upon one of the pistons to actuate it, and means coupling the second piston with the first piston for joint initial'advance of the two pistons on the compression stroke, said means cooperating with a part of the cylinder to release the first piston and to simultaneously lock the second piston to the cylinder after a predetermined advance of the first piston to permit,

durther advance of the first piston independently of the second piston, said second piston thereafter being restrained from movement in either direc- ,tion. r

'7. A fiuid pressure producing device comprising a cylinder, telescopic pistons reciprocable in the hollow piston having a pocket on its outer circumference, and means shiftabl in the pockets and aperture'for-locking the pistons together during a predetermined movement of the pistons and to thereafter release the pistons from one another and to" retain ERWIN F. LOWEKE.

one or the pistons against 

